Dr. Arti is an instructor in neurology, Harvard Medical School; and an assistant in neurology, Memory Disorders Unit and Department of Neurology, Massachusetts General Hospital, Boston, MA.
Choose the single best answer for each question.

Questions 1-3 refer to the following case study.

A 76-year-old retired English professor is brought to the clinic by her daughter, who reports that over the past 2 years her mother has had slowly progressing forgetfulness of recent conversations and events, peoples names, and the location of personal items. She also appears more withdrawn and less interested in longstanding social activities, but she enjoys her grandchildren, lives alone, drives locally, and manages her own finances. The patient denies being depressed or forgetful but admits to occasional senior moments. Her past medical history is significant for hypertension, and she takes a diuretic. Review of systems is negative. She has been widowed for 3 years and is a nonsmoker. She has had 1 or 2 mixed drinks in the evening for 30 years, but denies history of alcoholism. Her family history is significant for senility (mother) and stroke (brother). On examination, she is easily engaged, has sharp social wit, and has normal affect and mood. Mini-Mental State Exam (MMSE) score is 27/30 (-2 item recall, -1 date), and she has mildly diminished light touch, pinprick, cold, and vibration sensation in the feet. Otherwise, results of a general and elementary neurologic examination are unremarkable for her age. Results of laboratory tests are within normal limits except for a borderline (low-normal) vitamin B12 level.

1. What is the most likely primary cause of this patients presentation?

2. Suppose that a detailed assessment of the above patient shows normal basic and complex activities of daily living (ADL), neuropsychological (NP) testing reveals deficits only in learning and recall of new information, and magnetic resonance imaging (MRI) of the brain shows mild age-appropriate general cerebral atrophy and mild leukoaraiosis. Which of the following diagnoses would be consistent with this presentation?

3. Instead, suppose that the patient has had difficulty with planning large family meals and long trips, balancing her checkbook, and doing her taxes. NP testing shows not only deficits in new learning and remembering but also mild deficits in executive function, visuospatial function, and confrontational naming. Which of the following diagnoses would be consistent with this presentation?

4. A 67-year-old man with no significant past medical history, family history, or history of toxic exposure presents with a 1-year history of gradually increasing well-formed visual hallucinations, periods of confusion lasting minutes to hours, and increasing slowness of movement and imbalance. NP testing and examination show preserved memory function but moderate executive and visuospatial dysfunction, slowness of thought and general movements, and mildly diminished finger dexterity and postural reflexes. Results of laboratory tests and brain MRI are unremarkable. Electroencephalogram (EEG) shows mild bilateral posterior slowing but no spikes. A trial of carbidopa-levadopa did not improve his motor symptoms. What is this patients most likely diagnosis?